Field of the Invention
The present invention relates to the field of plasma generation devices or “plasma sources.”
Description of the Related Art
Plasma sources may be used in a variety of applications, including those requiring plasmas to be exposed directly to the open air. The applications include, for example, spray coating and materials synthesis and as an ignition aid in a hydrocarbon-fueled supersonic-combustor.
For a typical hydrocarbon-fueled supersonic combustor startup scenario, the fuel-air mixture will not auto-ignite and some ignition aid is therefore necessary to initiate main-duct combustion. The residence time through a typical combustion region is short, on the order of 1 millisecond (ms). Accordingly, means for reducing the ignition delay time and to increase the rate of combustion of hydrocarbon fuels are essential to the operation of the combustor. To fulfill these purposes, the igniter must provide adequate thermal energy to light the fuel and the delivered thermal energy should be able to deeply penetrate into the supersonic cross-flow.
Dense atmospheric-pressure plasma can be produced through dc/low frequency capacitive or high frequency inductive arc discharges, which require adding gas flows to stabilize the discharges and to carry the generated plasmas out of the discharge regions to form torches. The inductive torch and non-transferred dc torch employ high current power supply and require very high gas flow rate to achieve stable operation. Consequently, the structures of these torches are relatively large and are therefore unsuitable for certain applications. A typical torch module can run in dc or low frequency ac mode and can produce low power (hundreds of watts) or high power (a few kW in 60-Hz periodic mode or hundreds of kW in pulsed mode) plasma torches; however, the size of the plasma torch produced by such module is generally limited by the gap between the electrodes and depends strongly on the gas flow rate.
In view of the foregoing deficiencies of known plasma torches, there is a need for a plasma source that is portable and can generate a stable and sizable plasma torch independent of the gas flow rate.